This invention relates to lenses having multiple segments.
Different types of lenses are used in light sources, such as those in projector systems and in cameras. Referring to FIGS. 7A and 7B, one type of lens includes a fresnel lens 10, which is a thin, light-weight relatively planar lens that is formed by minute prisms 12 aligned in generally concentric grooves on a flat plate or sheet 11. A light source 30 is positioned behind the fresnel lens to shine light through the fresnel lens 10 to a target object 20 (which may be an object to be photographed by a camera or a screen used with a projector system, for example). The light source 30 may include a flash tube 32 and a reflector 34 to shine light onto the grooved side of the lens 10. The flat side 15 faces the target object 20.
With a typical fresnel lens, light non-uniformity may occur over the field of view. One such distortion involves a light distribution that is referred to as having a "dog bone" shape from the center to the edge of the field of view. Such distortion may adversely affect quality of images taken by a camera with strobe illumination or images projected on a screen by a projection system, as examples. The distortion may be attributed to the tube shadow of the flash tube 32 that forms part of the light source 30.
Thus, a need exist for a lens that can improve illumination uniformity characteristics of a light source.